The grass genera of the world

L. Watson, T.D. Macfarlane, and M.J. Dallwitz

Dimorphochloa S. T. Blake

~ Cleistochloa

Habit, vegetative morphology. Wiry, bushy perennial; caespitose. Culms 40–100 cm high; branched above. Culm nodes hairy. Culm internodes hollow. Young shoots extravaginal. Leaves not basally aggregated; non-auriculate. The sheaths short. Leaf blades narrow; not setaceous; rolled (short); not pseudopetiolate; without cross venation; disarticulating from the sheaths; rolled in bud. Ligule a fringe of hairs.

Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets. The spikelets of sexually distinct forms on the same plant (dimorphic, chasmogamous/cleistogamous). Plants exposed-cleistogamous and chasmogamous (the cleistogamous spikelets borne singly on short leafy shoots at the previous season’s nodes); without hidden cleistogenes.

Inflorescence. Inflorescence (chasmogamous, terminal) sparse, a single raceme, or paniculate; spatheate, or espatheate (according to interpretation of the limits of the inflorescence); a complex of ‘partial inflorescences’ and intervening foliar organs, or not comprising ‘partial inflorescences’ and foliar organs (according to interpretation). Spikelet-bearing axes ‘racemes’; with very slender rachides (these triquetous or compressed); persistent. Spikelets solitary; not secund; shortly pedicellate.

Female-fertile spikelets. Spikelets 4.7–5.2 mm long; adaxial; compressed dorsiventrally; falling with the glumes. Rachilla terminated by a female-fertile floret. Hairy callus absent.

Glumes one per spikelet, or two; very unequal; (the upper) long relative to the adjacent lemmas; free; dorsiventral to the rachis; hairy (G2, with short hairs on the back); awnless; very dissimilar (the lower minute to flimsy or absent, upper substantial and nearly equalling spikelet). Lower glume 0–1 nerved. Upper glume 5–7 nerved. Spikelets with incomplete florets. The incomplete florets proximal to the female-fertile florets. Spikelets with proximal incomplete florets. The proximal incomplete florets 1; sterile. The proximal lemmas awnless; 7 nerved; more or less equalling the female-fertile lemmas; becoming indurated, or not becoming indurated (tending to crustaceous).

Female-fertile florets 1. Lemmas decidedly firmer than the glumes; smooth; becoming indurated; entire; pointed; mucronate (the mucro incurved); hairless; non-carinate; with a clear germination flap; 5–7 nerved. Palea present; entire; 2-nerved. Lodicules present; 2; free; fleshy; glabrous. Stamens 3. Anthers about 2 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2; red pigmented.

Fruit, embryo and seedling. Fruit small (3–3.5 mm long); compressed dorsiventrally. Hilum short. Embryo large. Endosperm containing only simple starch grains. Embryo without an epiblast; with a scutellar tail; with an elongated mesocotyl internode.

Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells similar in shape costally and intercostally; of similar wall thickness costally and intercostally (fairly thin walled). Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type; 57–72 microns long; 8.4–10.5 microns wide at the septum. Microhair total length/width at septum 6.3–8.6. Microhair apical cells 27–34.5 microns long. Microhair apical cell/total length ratio 0.42–0.5. Stomata common; 36–39 microns long. Subsidiaries dome-shaped. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; not silicified. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies ‘panicoid-type’.

Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with radiate chlorenchyma, or with non-radiate chlorenchyma (rarely). Leaf blade ‘nodular’ in section; with the ribs more or less constant in size. Midrib not readily distinguishable; with one bundle only. Bulliforms present in discrete, regular adaxial groups; in simple fans. All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming ‘figures’. Sclerenchyma all associated with vascular bundles.

Classification. Watson & Dallwitz (1994): Panicoideae; Panicodae; Paniceae. Soreng et al. (2015): cf. Panicoideae (as a synonym?); Panicodae; Paniceae; Neurachninae. 1 species (D. rigida).

Distribution, phytogeography, ecology. Australia.

References, etc. Morphological/taxonomic: Blake 1941b. Leaf anatomical: studied by us.

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 11th December 2017.’.